U.S. patent number 6,602,656 [Application Number 10/225,608] was granted by the patent office on 2003-08-05 for silver halide imaging element with random color filter array.
This patent grant is currently assigned to Eastman Kodak Company. Invention is credited to Krishnan Chari, Dennis R. Perchak, Joel D. Shore.
United States Patent |
6,602,656 |
Shore , et al. |
August 5, 2003 |
Silver halide imaging element with random color filter array
Abstract
Disclosed is an imaging element comprising a single layer
containing a random distribution of a colored bead population of
one or more colors coated above one or more layers comprising light
sensitive silver halide emulsion grains, wherein the population
comprises beads of at least one color in which at least 25% (based
on projected area) of the beads of that color have an ECD less than
2 times the ECD of the silver halide grains in said one emulsion
layer or in the fastest emulsion layer in the case of more than one
emulsion layer
Inventors: |
Shore; Joel D. (Rochester,
NY), Chari; Krishnan (Fairport, NY), Perchak; Dennis
R. (Penfield, NY) |
Assignee: |
Eastman Kodak Company
(Rochester, NY)
|
Family
ID: |
27623150 |
Appl.
No.: |
10/225,608 |
Filed: |
August 22, 2002 |
Current U.S.
Class: |
430/511;
430/7 |
Current CPC
Class: |
G02B
5/201 (20130101); G03C 7/12 (20130101) |
Current International
Class: |
G02B
5/20 (20060101); G03C 7/04 (20060101); G03C
7/12 (20060101); G02B 005/20 (); G03C
001/825 () |
Field of
Search: |
;430/511,7 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: McPherson; John A.
Attorney, Agent or Firm: Kluegel; Arthur E.
Claims
What is claimed is:
1. An imaging element comprising a single layer containing a random
distribution of a colored bead population of one or more colors
coated above one or more layers comprising light sensitive silver
halide emulsion grains, wherein the bead population comprises beads
of at least one color in which at least 25% (based on projected
area) of the beads of that color have an ECD less than 2 times the
ECD of the silver halide grains in said one emulsion layer or in
the fastest emulsion layer in the case of more than one emulsion
layer.
2. The element of claim 1 wherein the bead population comprises
beads of two or more colors.
3. The element of claim 2 wherein at least two of the bead colors
comprise beads in which at least 25% (based on projected area) of
the beads have an ECD less than 2 times the ECD of the silver
halide grains in said one emulsion layer or in the fastest emulsion
layer in the case of more than one emulsion layer.
4. The element of claim 3 wherein the beads comprise three colors
and the three bead colors comprise beads in which at least 25%
(based on projected area) of the beads have an ECD less than 2
times the ECD of the silver halide grains in said one emulsion
layer or in the fastest emulsion layer in the case of more than one
emulsion layer.
5. The element of claim 2 wherein the beads of all colors combined,
in toto, comprise beads in which at least 25% (based on projected
area) of the beads have an ECD less than 2 times the ECD of the
silver halide grains in said one emulsion layer or in the fastest
emulsion layer in the case of more than one emulsion layer.
6. The element of claim 1 in which at least 30% (based on projected
area) of the beads of said at least one color have an ECD less than
2 times the ECD of the silver halide grains in said one emulsion
layer or in the fastest emulsion layer in the case of more than one
emulsion layer.
7. The element of claim 1 in which at least 50% (based on projected
area) of the beads of said at least one color have an ECD less than
2 times the ECD of the silver halide grains in said one emulsion
layer or in the fastest emulsion layer in the case of more than one
emulsion layer.
8. The element of claim 1 in which the beads are green.
9. The element of claim 1 in which at least 50% (based on projected
area) of the beads of said at least one color have an ECD of from
0.5 to 3 times the ECD of the silver halide grains in said one
emulsion layer or in the fastest emulsion layer in the case of more
than one emulsion layer.
10. The element of claim 9 in which at least 50% (based on
projected area) of the beads of said at least one color have an ECD
of from 1 to 2 times the ECD of the silver halide grains in said
one emulsion layer or in the fastest emulsion layer in the case of
more than one emulsion layer.
11. The element of claim 1 in which at least 75% (based on
projected area) of the beads of said at least one color have an ECD
of from 0.5 to 3 times the ECD of the silver halide grains in said
one emulsion layer or in the fastest emulsion layer in the case of
more than one emulsion layer.
12. The element of claim 1 in which the ECD of the silver halide
grains either comprising said one layer or comprising the fastest
layer of more than one layer is less than 3 micrometers.
13. The element of claim 1 comprising a support located on the side
of the one or more layers of silver halide emulsion grains opposite
from the layer containing the random distribution of colored
beads.
14. The element of claim 1 comprising a support located between the
one or more layers of silver halide emulsion grains and the layer
containing the random distribution of colored beads.
15. The element of claim 1 wherein the light sensitive silver
halide grains are not color sensitized.
16. The element of claim 1 wherein the bead containing layer
exhibits not more than 20% overlap.
17. A process for forming an image comprising imagewise exposing
the element of claim 1 and thereafter contacting the silver halide
emulsion with a reducing agent to form an image.
18. The process of claim 17 wherein the image is scanned via color
selective light transmission of the beads after development.
Description
FIELD OF THE INVENTION
This invention relates to an imaging element comprising a layer
containing a random distribution of colored beads of one or more
colors coated above one or more layers of silver halide emulsion
grains, wherein the bead population comprises beads of at least one
color in which at least 25% (based on projected area) of the beads
of that color have an ECD less than 2 times the ECD of the silver
halide grains either comprising said one layer or comprising the
fastest layer of more than one layer.
BACKGROUND OF THE INVENTION
The great majority of color photographs today are taken using
chromogenic color film in which color-forming couplers, which may
be incorporated in the film or present in the processing solution,
form cyan, magenta and yellow dyes by reaction with oxidized
developing agent which is formed where silver halide is developed
in an imagewise pattern. Such films require a development process
which is carefully controlled in respect of time and temperature,
which is usually followed by a silver bleaching and a fixing step,
and the whole process typically takes several minutes and needs
complex equipment.
Color photography by exposing a black-and-white photographic
emulsion through a color filter array which is an integral part of
the film or plate on which the photographic emulsion is coated, has
long been known to offer certain advantages of simplicity or
convenience in color photography. Thus the Autochrome process,
disclosed by the Lumiere brothers in 1906 (U.S. Pat. No. 822,532)
exposed the emulsion through a randomly disposed layer of red,
green and blue-colored potato starch grains, and the emulsion was
reversal processed to give a positive image of the scene which
appeared colored when viewed by light transmitted through the
plate. The process allowed the formation of a colored photograph
without the chemical complexity of later photographic methods.
The Dufaycolor process (initially the Dioptichrome plate, L.Dufay,
1909) used a regular array of red, green and blue dyed patches and
lines printed on a gelatin layer in conjunction with a
reversal-processed black-and-white emulsion system, which similarly
gave a colored image of the scene when viewed by transmitted
light.
Polavision (Edwin Land and the Polaroid Corporation, 1977) was a
color movie system employing a rapid and convenient reversal
processing method on a black-and-white emulsion system coated above
an array of red, green and blue stripes, which gave a colored
projected image. It was marketed as a still color transparency
system called Polachrome in 1983.
These methods suffered a number of disadvantages. The images were
best viewed by passing light through the processed film or plate,
and the image quality was not sufficient to allow high quality
prints to be prepared from them, due to the coarse nature of the
Autochrome and Dufaycolor filter arrays, and the coarse nature of
the positive silver image in the Polavision and Polacolor systems.
The regular array patterns were complicated and expensive to
manufacture. In addition, the films which used regular or repeating
filter arrays were susceptible to color aliasing when used to
photograph scenes with geometrically repeating features.
U.S. Pat. No. 4,971,869 discloses a film with a regular repeating
filter array which claims to be less susceptible to aliasing
problems. The film comprises a panchromatic photographic emulsion
and a repetitive pattern of a unit of adjacent colored cells
wherein at least one of the cells is of a subtractive primary color
(e.g. yellow, magenta or cyan) or is of a pastel color. Scene
information can be extracted from the developed film by
opto-electronic scanning methods.
U.S. Pat. No. 6,117,627 discloses a light sensitive material
comprising a transparent support having thereon a silver halide
emulsion layer and a randomly arranged color filter layer
comprising colored resin particles. The material has layer
arrangement limitations and results in increased fogging of the
sensitized layer. The patent discloses the preparation of a color
filter array using heat and pressure to form the color filter layer
prior to application of the light sensitive layer to a support. Due
to the necessary use of pressure and heat, it is not practical to
use the teachings of this patent to prepare a film having a light
sensitive layer between the color filter layer and the support.
Attempting to apply the needed heat and pressure to bond the filter
layer to the rest of the multilayer would damage the light
sensitive layer. The patent also discloses exposing, processing and
electro-optically scanning the resultant image in such a film and
reconstructing the image by digital image processing.
Color photographic films which comprise a color filter array and a
single image recording layer or layer pack have the advantage of
rapid and convenient photographic processing, as the single image
recording layer or layer pack can be processed rapidly without the
problem of mismatching different color records if small variations
occur in the process. A small change in extent of development for
example will affect all color records equally. Exceptionally rapid
processing is possible using simple negative black-and-white
development, and if suitable developing agents are included in the
coating, the photographic response can be remarkably robust or
tolerant towards inadvertent variations in processing time or
temperature.
Copending and commonly assigned U.S. Ser. No. 09/922,273, filed
Aug. 3, 2001, the contents of which are incorporated herein by
reference, discloses a color film comprising (1) a support layer,
(2) a light sensitive layer, and (3) a water permeable color filter
array (CFA) layer comprising a continuous phase transparent binder
containing a random distribution of colored transparent beads, said
beads comprising a water-immiscible synthetic polymer or
copolymer.
An undesirable feature of the random color filter array in general
is the introduction of noise into the imaging system due to the
randomness of the array. For the purposes of illustration, consider
the case of a system with three bead colors, red, green, and blue,
although the ideas to be discussed hold independent of this
specific embodiment. Define the average projected areal coverage of
beads of each color is <r>, <g>, and <b> for red,
green, and blue beads, respectively. If one considers a certain
aperture size corresponding, for example, to the aperture size of a
scanning device used to scan this film, then because of random
fluctuations the actual areal coverages of the beads in this
aperture region, r, g, and b, will not in general be exactly equal
to the above average values. Rather, as the aperture is scanned
over the array, the values of r, g, and b will fluctuate about the
average values of <r>, <g>, and <b>. It is
desirable to minimize the magnitude of these fluctuations in areal
coverage.
It is well-understood from basic statistical considerations that,
for a given aperture size, the noise (i.e., the magnitude of these
fluctuations) will decrease as the size of all of the beads, in
toto, is made smaller. However, if the system contains beads with a
distribution of sizes, it is not clear to what extent reducing the
size of only a portion of the beads will reduce the noise. In
particular, it is not clear to what extent reducing the size of
only the beads of a certain color or colors will reduce the noise.
This latter question is important because manufacturability issues,
such as the ability to load dye into the beads, may set a lower
limit on the size of one or more colors of the beads. While
reducing the noise level is a goal, it is desirable to achieve that
objective without causing undesirable effects on the imaging system
as a whole because, if the beads become too small relative to the
underlying emulsion grains, then it is expected that the quality of
the color reproduction will be sacrificed (and the noise of the
imaging system as a whole may even be increased).
Japanese published application 09-145,909 discloses the use of a
silver halide material as a means of placing colored filter
elements on a liquid crystal display. U.S. Pat. No. 5,998,109
discloses a light sensitive silver halide material containing at
least three stripe-like or mosaic layers having different spectral
transmission characteristics. This patent is unclear as to how the
three layers are arranged. Moreover, this patent does not address
the issue of controlling the noise level of the image information.
It gives broad ranges of filter and grain sizes but does not
address the importance of selecting the relative sizes on the
resulting noise levels.
It is a problem to be solved to provide a silver halide emulsion
film employing colored beads wherein the size of the beads is
selected relative to the silver halide grain size so that the noise
level is reduced.
SUMMARY OF THE INVENTION
The invention provides an imaging element comprising a single layer
containing a random distribution of a colored bead population of
one or more colors coated above one or more layers comprising light
sensitive silver halide emulsion grains, wherein the population
comprises beads of at least one color in which at least 25% (based
on projected area) of the beads of that color have an ECD less than
2 times the ECD of the silver halide grains in said one emulsion
layer or in the fastest emulsion layer in the case of more than one
emulsion layer. The invention also provides an imaging process
employing the imaging element.
Embodiments of the invention provide a silver halide emulsion film
employing colored beads wherein the size of the beads is selected
so that the noise level is reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of the layers of one embodiment of the
invention.
FIG. 2 is a schematic view of the layers of a second embodiment of
the invention.
FIG. 3 is a schematic view of the layers of a third embodiment of
the invention.
FIG. 4 is a schematic view of a film according to a fourth
embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
In the discussion below, we will for illustrative purposes consider
the case of a film consisting of a random color filter array (CFA)
containing three different color beads, specifically red, green,
and blue. However, it is understood that the discussion could
easily be generalized to other CFA configurations.
As used herein the following terms are as defined: "bead" means a
solid or liquid particle having a substantially curvilinear shape.
Examples of beads are particles having a spheroid or ellipsoid
shape. Particles with substantial edges or corners or which have
been crushed, powdered or ground are not beads. The beads may
comprise a polymer that is inherently colored or may contain a
separate colorant. "a color" refers to hues of "blue", "green" and
"red" having maximum absorptions in the range of 400-500nm,
500-600nm, and 600-700nm, respectively. "insoluble colorant" means
a colorant, whether a pigment or a dye, that is not dissolved under
either the coating conditions for making the film or the
development conditions for processing the film. "light sensitive
layer" means a layer that, upon imagewise exposure to light,
undergoes more or less change depending on the amount of light
exposure. "nano-particle" means a particle having an average
particle size less than 0.3 microns. "nano-particulate milled
dispersion" means a nano-particle dispersion prepared by milling.
"percentage overlap" means the ratio of (the projected overlapping
cross-section of overlapping beads divided by the cross-section of
all beads).times.100. More accurate imaging and more light
sensitivity occurs when a given photon of light is filtered by only
one color of bead. A high percentage overlap is therefore an
undesirable feature of CFA. "synthetic polymer" means a polymer
prepared from the corresponding monomers by synthetic means as
opposed to one occurring in nature, such as gelatin. "water
permeable layer" means a layer that is readily pervious to
water.
The invention provides an imaging element as summarized above. The
element desirably comprises beads of two or more colors or even
three or more colors wherein at least two of the bead colors
comprise beads in which at least 25% (based on projected area) of
the beads have an ECD less than 2 times the ECD of the silver
halide grains in said one emulsion layer or in the fastest emulsion
layer in the case of more than one emulsion layer. Desirably, the
beads may comprise three colors and the three bead colors comprise
beads in which at least 25% (based on projected area) of the beads
have an ECD less than 2 times the ECD of the silver halide in said
one emulsion layer or in the fastest emulsion layer in the case of
more than one emulsion layer. Considering all colors combined, in
toto, the population may comprise beads in which at least 25%
(based on projected area) of the beads have an ECD less than 2
times the ECD of the silver halide in said one emulsion layer or in
the fastest emulsion layer in the case of more than one emulsion
layer.
Suitably, at least 30% (based on projected area), and desirably at
least 50% of the beads of the one color have an ECD less than 2
times the ECD of the silver halide grains either comprising said
one layer or comprising the fastest layer of more than one layer.
The film of the invention conveniently employs the desired sized
beads in a green population.
The film of the invention may employ at least 50% or even at least
75% (based on projected area) of the beads of said at least one
color that have an ECD of from 0.5 to 3 times or even 1 to 2 times
the ECD of the silver halide grains in said one emulsion layer or
in the fastest emulsion layer in the case of more than one emulsion
layer.
The film of the invention desirably comprises silver halide grains
in said one emulsion layer or in the fastest emulsion layer in the
case of more than one emulsion layer with an ECD that is less than
3 micrometers. The film may comprise a support located on the side
of the one or more layers of silver halide emulsion grains opposite
from the layer containing the random population of colored beads or
a support located between the one or more layers of silver halide
emulsion grains and the layer containing the random population of
colored beads.
The invention also provides an imaging process for forming an image
comprising imagewise exposing the film of the invention and
thereafter contacting the silver halide emulsion with a reducing
agent to form an image. Suitably, the process includes the
subsequent step of printing the image via color selective light
transmission of the beads after development.
Besides the limitations above, for particular situations there may
be further constraints on the size of the beads set by
manufacturability issues, such as (but not limited to) the ability
to load dye into the beads.
FIG. 1 shows one embodiment useful with the film of the invention.
The multilayer color film comprises support 1 bearing light
sensitive layer 2, an underlayer 3, color filter array (CFA) layer
4, protective overcoat 5, the CFA layer containing transparent
beads of a first color 6 and second color 7 disposed in a water
permeable continuous phase transparent binder 9. The thicknesses of
the layers are not to scale.
FIG. 2 shows a similar multilayer structure in which there are also
beads 8 of a third color in layer 4.
FIG. 3 shows a multilayer similar to that of FIG. 2 additionally
containing neutral nano-particles 10 dispersed in the continuous
phase transparent binder 9.
FIG. 4 shows a multilayer similar to that of FIG. 3 in which the
layer order is rearranged to place layers 2 and 4 on opposite sides
of the support.
The beads useful in the invention may be solid or liquid in
character. They are curvilinear in shape to aid in the formation of
a bead containing monolayer having a low percentage overlap (not
more than 20% overlap) with color particles of other colors. They
may be prepared in any manner suitable for obtaining the desired
bead shape. Suitable methods are suspension and emulsion
polymerization methods such as the limited coalescence technique as
described by Thomas H. Whitesides and David S. Ross in "J. Colloid
Interface Science" 169. 48-59 (1995).
The limited coalescence method includes the "suspension
polymerization" technique and the "polymer suspension" technique. A
preferred method of preparing polymer particles in accordance with
this invention is by a limited coalescence technique where
poly-addition polymerizable monomer or monomers are added to an
aqueous medium containing a particulate suspending agent to form a
discontinuous (oil droplet) phase in a continuous (water) phase.
The mixture is subjected to shearing forces, by agitation,
homogenization and the like to reduce the size of the droplets.
After shearing is stopped, an equilibrium is reached with respect
to the size of the droplets as a result of the stabilizing action
of the particulate suspending agent in coating the surface of the
droplets, and then polymerization is completed to form an aqueous
suspension of polymer particles. This process is described in U.S.
Pat. Nos. 2,932,629; 5,279,934; and 5,378,577; which are
incorporated herein by reference.
In the "polymer suspension" technique, a suitable polymer is
dissolved in a solvent and this solution is dispersed as fine
water-immiscible liquid droplets in an aqueous solution that
contains colloidal silica as a stabilizer. Equilibrium is reached
and the size of the droplets is stabilized by the action of the
colloidal silica coating the surface of the droplets. The solvent
is removed from the droplets by evaporation or other suitable
technique resulting in polymeric particles having a uniform coating
thereon of colloidal silica. This process is further described in
U.S. Pat. No. 4,833,060 issued May 23, 1989, incorporated by
reference.
In practicing this invention using the suspension polymerization
technique, any suitable monomer or monomers may be employed such
as, for example, styrene, vinyl toluene, p-chlorostyrene; vinyl
naphthalene; ethylenically unsaturated mono-olefins such as
ethylene, propylene, butylene and isobutylene; vinyl halides such
as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate,
vinyl propionate, vinyl benzoate and vinyl butyrate; esters of
alpha-methylene aliphatic monocarboxylic acids such as methyl
acrylate, ethyl acrylate, n-butylacrylate, isobutyl acrylate,
dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl
acrylate, methyl-alpha-chloroacrylate, methyl methacrylate, ethyl
methacrylate and butyl methacrylate; acrylonitrile,
methacrylonitrile, acrylamide, vinyl ethers such as vinyl methyl
ether, vinyl isobutyl ether and vinyl ethyl ether; vinyl ketones
such as vinyl methylketone, vinyl hexyl ketone and methyl isopropyl
ketone; vinylidene halides such as vinylidene chloride and
vinylidene chlorofluoride; and N-vinyl compounds such as N-vinyl
pyrrole, N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone
divinyl benzene, ethylene glycol dimethacrylate, mixtures thereof;
and the like.
In the suspension polymerization technique, other addenda are added
to the monomer droplets and to the aqueous phase of the mass in
order to bring about the desired result including initiators,
promoters and the like which are more particularly disclosed in
U.S. Pat. Nos. 2,932,629 and 4,148,741, both of which are
incorporated herein by reference.
Useful solvents for the polymer suspension process are those that
dissolve the polymer, which are immiscible with water and which are
readily removed from the polymer droplets such as, for example,
chloromethane, dichloromethane, ethylacetate, vinyl chloride,
methyl ethyl ketone, trichloromethane, carbon tetrachloride,
ethylene chloride, trichloroethane, toluene, xylene, cyclohexanone,
2-nitropropane and the like. A particularly useful solvent is
dichloromethane because it is a good solvent for many polymers
while at the same time, it is immiscible with water. Further, its
volatility is such that it can be readily removed from the
discontinuous phase droplets by evaporation.
The quantities of the various ingredients and their relationship to
each other in the polymer suspension process can vary over wide
ranges, however, it has generally been found that the ratio of the
polymer to the solvent should vary in an amount of from about 1 to
about 80% by weight of the combined weight of the polymer and the
solvent and that the combined weight of the polymer and the solvent
should vary with respect to the quantity of water employed in an
amount of from about 25 to about 50% by weight. The size and
quantity of the colloidal silica stabilizer depends upon the size
of the particles of the colloidal silica and also upon the size of
the polymer droplet particles desired. Thus, as the size of the
polymer/solvent droplets are made smaller by high shear agitation,
the quantity of solid colloidal stabilizer is varied to prevent
uncontrolled coalescence of the droplets and to achieve uniform
size and narrow size distribution of the polymer particles that
result. These techniques provide particles having a predetermined
average diameter anywhere within the range of from 0.5 micrometer
to about 150 micrometers with a very narrow size distribution. The
coefficient of variation (ratio of the standard deviation to the
average diameter, as described in U.S. Pat. No. 2,932,629) is
normally in the range of about 15 to 35%.
The particular polymer employed to make the beads is a water
immiscible synthetic polymer that may be colored. The preferred
polymer is any amorphous water immiscible synthetic polymer.
Examples of polymer types that are useful are polystyrene,
poly(methyl methacrylate) or poly(butyl acrylate). Copolymers such
as a copolymer of styrene and butyl acrylate may also be used.
Polystyrene polymers are conveniently used. The formed beads are
colored using an insoluble colorant that is a pigment or dye that
is not dissolved under either the coating conditions or the
development processing conditions. Suitable dyes may be oil-soluble
in nature, and can be chosen for example from the classes of
solvent dyes and disperse dyes listed in the Color Index, 3rd
Edition, published by The Society of Dyers and Colorists, Bradford,
England. Specific examples are listed under their Color Index (CI)
names, and include CI Solvent Blue 14, CI Solvent Blue 35, CI
Solvent Blue 63, CI Solvent Blue 79, CI Solvent Yellow 174, CI
Solvent Orange 1, CI Solvent Red 19, CI Solvent Red 24, CI Disperse
Yellow 3, and 4-phenylazodiphenylamine.
Suitable pigments are chosen for their properties of hue, fastness,
and colorability, and can include, for example, CI Pigment Green 7,
CI Pigment Green 36, CI Pigment Blue 15:3, CI Pigment Blue 60, CI
Pigment Violet 23, CI Pigment Red 122, CI Pigment Red 177, CI
Pigment Red 194, CI Pigment Orange 36, CI Pigment Orange 43, CI
Pigment Yellow 74, CI Pigment Yellow 93, CI Pigment Yellow 110, and
CI Pigment Yellow 139. When pigment particles are incorporated in
the colored elements, they should be of a fine.particle size,
preferably substantially less than one micrometer.
After the beads are colored, they are then randomly mixed with
other beads similarly prepared but dyed a different color. The
beads are desirably formed so as to have an equivalent circular
diameter, when projected in a direction perpendicular to the
support, of 3-15 micrometers.
The beads are conveniently dispersed in a random manner into a
continuous transparent binder. The binder is any water permeable
material that will permit water to pass through the layer in the
development-processing phase of the imaging. Examples of suitable
water permeable binders include gelatin, poly(vinyl alcohol),
poly(vinyl pyrrolidone), poly(ethylene oxide), polyacrylamide,
polymers based on acrylic acid or maleic acid units, and water
soluble cellulose derivatives such as hydroxyethyl cellulose.
Gelatin is a readily convenient source for the water permeable
binder
Improved quality reproductions are obtained when the binder
contains an additional neutral colored particle. Such particles may
range from white to black and are desirable of a mean size smaller
than the beads so as to enable the particles to fill voids between
the beads. Nano-particles having an average particle size in the
range of 0.01 to 0.3 microns are useful for this purpose. Carbon
black is one suitable composition for this nano-particle.
Commercially available carbon samples (e.g., Black Pearls 280,
Black Pearls 430, Black Pearls 490, Black Pearls 700, Black Pearls
880, Black Pearls 1000, Regal 250, Regal 350, and Regal 400
available from Cabot Corp.) may be obtained and milled in
accordance with conventional procedures (e.g., in accordance with
the milling process described in U.S. Pat. No. 5,500,331) to obtain
desired dispersed particle size.
The beads in the continuous phase transparent binder may also
contain a cross-linking agent but this component will desirably be
less than 30 wt % of the total polymer content. The beads will
typically be composed of beads of two or more colors. Three or more
colors provide better color rendition in general. An additive or
subtractive primary system may serve as the basis for the bead
colors. Thus, either red/green/blue or cyan/magenta/yellow systems
may be readily used.
Passage of processing solutions and chemicals through the CFA layer
is especially important in the preferred film structure in which
the CFA is located between the emulsion layers and the top coated
surface of the film, that is between the emulsion layers and the
processing solutions which are applied to the film, see FIGS. 1-3.
This film structure is preferred because it allows the film to be
exposed in the camera with the support towards the back of the
camera and the emulsion side toward the lens, which is the
orientation for which films and cameras are normally designed. Such
a film structure is essential in the case of Advanced Photographic
System films because the magnetic recording layer functions most
effectively when coated on the back of the support and has to be in
contact with the magnetic heads in the back of the camera. It may
be desirable to provide an undercoat for the CFA layer to help
control the extent of monolayer coating of the beads. It is further
desirable to provide an overcoat over the CFA layer for protective
purposes.
The light sensitive layer 2 may comprise one or more layers. The
light sensitive portions are sensitive to light that has
successfully passed through the layers above it. Thus the image
information for each color record is recorded in the light
sensitive layer or emulsion layer unit. The layers may be of
differing light sensitivities or speeds. Photographic addenda known
in the art, such as antifoggants and speed-increasing agents may be
present in or adjacent to the layer(s) 3. Substances such as
developing agents, blocked developing agents, color couplers and
other materials which take part in the processing step may be in or
adjacent to the emulsion layer(s) 3. Developing agents suitable for
including in the coating, and a preferred way of incorporating
them, are disclosed in U.S. Pat. No. 5,804,359.
The light sensitive layer is desirably one based on a silver halide
emulsion of the type common in the art. The particular type of
emulsion and development processing employed is not critical so any
of the emulsion types and development processes available may be
used. The emulsion is panchromatically sensitized so that it is
sensitive to any color light that is transmitted by the nearby
filter beads. The image is suitably formed by the developed silver
using either a negative or reversal process.
The black-and-white photographic silver halide elements useful in
the present invention are generally composed of a conventional
flexible, transparent film support (polyester, cellulose acetate or
polycarbonate) that has applied to each side one or more
photographic silver halide emulsion layers. For some uses, it is
conventional to use blue-tinted support materials to contribute to
the blue-black image tone sought in fully processed films.
Polyethylene terephthalate and polyethylene naphthalate are
suitable film supports.
In general, such elements, emulsions, and layer compositions are
described in many publications, including Research Disclosure,
publication 36544, September 1994. Research Disclosure is a
publication of Kenneth Mason Publications, Ltd., Dudley House, 12
North Street, Emsworth, Hampshire PO10 7DQ England.
The support can take the form of any conventional element support.
Useful supports can be chosen from among those described in
Research Disclosure, September 1996, Item 38957 XV. Supports and
Research Disclosure, Vol. 184, August 1979, Item 18431, XII. Film
Supports. They can be transparent or translucent polymeric film
supports, or opaque cellulose papers or media. In its simplest
possible form the film support consists of a material chosen to
allow direct adhesion of the hydrophilic silver halide emulsion
layers or other hydrophilic layers. More commonly, the support is
itself hydrophobic and subbing layers are coated thereon to
facilitate adhesion of the hydrophilic silver halide emulsion
layers.
The photographic materials include one or more silver halide
emulsion layers that comprise one or more types of silver halide
grains responsive to suitable electromagnetic radiation. Such
emulsions include silver halide grains composed of, for example,
silver bromide, silver iodobromide, silver chlorobromide, silver
iodochlorobromide, and silver chloroiodobromide, or any
combinations thereof. The silver halide grains in each silver
halide emulsion layer or unit can be the same or different, or
mixtures of different types of grains.
The silver halide grains can have any desired morphology (for
example, cubic, tabular, octahedral), or mixtures of grains of
various morphologies. In some embodiments, at least 50% (sometimes
at least 70%) of the silver halide grain projected area is provided
by tabular grains having an average aspect ratio greater than 8, or
greater than 12.
Imaging contrast can be raised by the incorporation of one or more
contrast enhancing dopants. Rhodium, cadmium, lead and bismuth are
all well known to increase contrast by restraining toe development.
Rhodium is most commonly employed to increase contrast and is
specifically preferred.
A variety of other dopants are known individually and in
combination, to improve contrast as well as other common
properties, such as speed and reciprocity characteristics. Dopants
capable providing "shallow electron trapping" sites commonly
referred to as SET dopants are specifically contemplated. SET
dopants are described in Research Disclosure, Vol. 367, Nov. 1994,
Item 36736. Iridium dopants are very commonly employed to decrease
reciprocity failure. A summary of conventional dopants to improve
speed, reciprocity and other imaging characteristics is provided by
Research Disclosure, Item 36544, cited above, Section I. Emulsion
grains and their preparation, sub-section D. Grain modifying
conditions and adjustments, paragraphs (3), (4) and (5).
Low coefficient of variation (COV) emulsions can be selected from
among those prepared by conventional batch double-jet precipitation
techniques. A general summary of silver halide emulsions and their
preparation is provided by Research Disclosure, Item 36544, cited
above, Section I. Emulsion grains and their preparation. After
precipitation and before chemical sensitization the emulsions can
be washed by any convenient conventional technique using techniques
disclosed by Research Disclosure, Item 36544, cited above, Section
III. Emulsion washing.
The emulsions can be chemically sensitized by any convenient
conventional technique as illustrated by Research Disclosure, Item
36544, Section IV. Sulfur and gold sensitization is specifically
contemplated.
Instability which increases minimum density in negative-type
emulsion coatings (i.e., fog) can be protected against by
incorporation of stabilizers, antifoggants, antikinking agents,
latent image stabilizers and similar addenda in the emulsion and
contiguous layers prior to coating. Such addenda are illustrated by
Research Disclosure, Item 36544, Section VII and Item 18431,
Section II.
The silver halide emulsion and other layers forming the layers on
the support contain conventional hydrophilic colloid vehicles
(peptizers and binders) that are typically gelatin or a gelatin
derivative (identified herein as "gelatino-vehicles"). Conventional
gelatino-vehicles and related layer features are disclosed in
Research Disclosure, Item 36544, Section II. Vehicles, vehicle
extenders, vehicle-like addenda and vehicle related addenda. The
emulsions themselves can contain peptizers of the type set out in
Section II noted above, paragraph A. Gelatin and hydrophilic
colloid peptizers. The hydrophilic colloid peptizers are also
useful as binders and hence are commonly present in much higher
concentrations than required to perform the peptizing function
alone. The gelatino-vehicle extends also to materials that are not
themselves useful as peptizers. The preferred gelatino-vehicles
include alkali-treated gelatin, acid-treated gelatin or gelatin
derivatives (such as acetylated gelatin and phthalated gelatin).
Depending upon the use of the materials, the binder-containing
layers can be hardened or unhardened.
Some photographic materials can include a surface overcoat on each
side of the support that are typically provided for physical
protection of the emulsion layers. In addition to vehicle features
discussed above the overcoats can contain various addenda to modify
the physical properties of the overcoats. Such addenda are
illustrated by Research Disclosure, Item 36544, Section IX. Coating
physical property modifying addenda, A. Coating aids, B.
Plasticizers and lubricants, C. Antistats, and D. Matting agents.
Interlayers that are typically thin hydrophilic colloid layers can
be used to provide a separation between the emulsion layers and the
surface overcoats. It is quite common to locate some emulsion
compatible types of surface overcoat addenda, such as anti-matte
particles, in the interlayers.
Processing the black and white element generally involves the steps
of developing, fixing, washing, and drying. Processing can be
carried out in any suitable processor or processing container for a
given type of photographic element (for example, sheets, strips or
rolls). The photographic material is generally bathed in the
processing compositions for a suitable period of time.
The photographic developing composition includes at least one of
the conventional developing agents utilized in black-and-white
processing. Such developing agents include dihydroxybenzene
developing agents, ascorbic acid developing agents, aminophenol
developing agents, and 3-pyrazolidone developing agents. The
dihydroxybenzene developing agents which can be employed in the
developing compositions are well known and widely used in
photographic processing. The preferred developing agent of this
class is hydroquinone. Other useful dihydroxybenzene developing
agents include: chlorohydroquinone, bromohydroquinone,
isopropylhydroquinone, toluhydroquinone, methylhydroquinone,
2,3-dichlorohydroquinone, 2,5-dimethylhydroquinone,
2,3-dibromohydroquinone,
1,4-dihydroxy-2-acetophenone-2,4-dimethylhydroquino- ne
2,5-diethylhydroquinone, 2,5-di-p-phenethylhydroquinone,
2,5-dibenzoylaminohydroquinone, and 2,5-diacetaminohydroquinone.
Ascorbic acid developing agents have also been utilized heretofore
in a wide variety of photographic developing processes as shown in
U.S. Pat. Nos. 2,688,548; 2,688,549; 3,022,168; 3,512,981;
3,870,479; 3,942,985; 4,168,977; 4,478,928; and 4,650,746.
Developing compositions which utilize a primary developing agent,
such as a dihydroxybenzene developing agent or an ascorbic acid
developing agent, frequently also contain an auxiliary
super-additive developing agent. Examples of useful auxiliary
super-additive developing agents are aminophenols and
3-pyrazolidones. The auxiliary super-additive developing agents
which can be employed in the developing compositions of are
well-known and widely used in photographic processing.
In addition to one or more developing agents, the developing
compositions usually also contain a sulfite preservative. By the
term "sulfite preservative" as used herein is meant any sulfur
compound that is capable of forming sulfite ions in aqueous
alkaline solution. Examples of such compounds include alkali metal
sulfites, alkali metal bisulfites, alkali metal metabisulfites,
sulfurous acid and carbonyl-bisulfite adducts. Examples of
preferred sulfites for use in the developing solutions of this
invention include sodium sulfite, potassium sulfite, lithium
sulfite, sodium bisulfite, potassium bisulfite, lithium bisulfite,
sodium metabisulfite, potassium metabisulfite, and lithium
metabisulfite. The carbonyl-bisulfite adducts are well-known
compounds . Adducts of adehydes and adducts of ketones are useful
and the adlehydes employed can be monoaldehydes, dialdehydes or
trialdehydes and the ketones can be monoketones, diketones or
triketones. The bisulfite adducts can be adducts of alkali metal
bisulfites, alkaline earth metal bisulfites or nitrogen-base
bisulfites such as amine bisulfites. Illustrative examples of the
many carbonyl-bisulfite adducts which are useful in the present
invention include the following compounds (all of those listed
being sodium bisulfite adducts for the purpose of convenience in
illustrating the invention, but it being understood that the
compounds can also be employed in the form of adducts of other
suitable bisulfites as explained herein-above): sodium formaldehyde
bisulfite sodium acetaldehyde bisulfite sodium propionaldehyde
bisulfite sodium butyraldehyde bisulfite succinaldehyde bis-sodium
bisulfite glutaraldehyde bis-sodium bisulfite beta-methyl
glutaraldehyde bis-sodium bisulfite maleic dialdehyde bis-sodium
bisulfite sodium acetone bisulfite sodium butanone bisulfite sodium
pentanone bisulfite 2,4-pentandione bis-sodium bisulfite, and the
like. Alkaline agents whose functions is to control pH, such as
carbonates, phosphates, amines or borates, are preferably also
included in the developing compositions. The amount of primary
developing agent incorporated in the working strength developing
solution can vary widely as desired. Typically, amounts of from
about 0.05 to about 1.0 moles per liter are useful. Typically,
amounts in the range of from 0.1 to 0.5 moles per liter are
employed. The amount of auxiliary super-additive developing agent
utilized in the working strength developing solution can vary
widely as desired. Usually, amounts of from about 0.001 to about
0.1 moles per liter are useful. Typically, amounts in the range of
from 0.002 to 0.01 moles per liter are employed. The amount of
sulfite preservative utilized in the working strength developing
solution can vary widely as desired. Typically, amounts of from
about 0.05 to about 1.0 moles per liter are useful. Amounts in the
range of from 0.1 to 0.5 moles per liter are commonly employed.
Working strength developing solutions prepared from the developing
compositions of this invention typically have a pH in the range of
from 8 to 13 and preferably in the range of from 9 to 11.5.
Typically, the development temperature can be any temperature
within a wide range as known by one skilled in the art, for example
from about 15 to about 50.degree. C.
A variety of other optional ingredients can also be advantageously
included in the developing composition. For example, the developing
composition can contain one or more antifoggants, antioxidants,
sequestering agents, stabilizing agents or contrast-promoting
agents. Examples of particularly useful contrast-promoting agents
are amino compounds as described, for example, in U.S. Pat. No.
4,269,929. Examples of useful stabilizing agents are
.beta.-ketocarboxylic acids as described, for example, in U.S. Pat.
No. 4,756,997.
In most processing methods, the developing step is generally
followed by a fixing step using a photographic fixing composition
containing a photographic fixing agent. While sulfite ion sometimes
acts as a fixing agent, the fixing agents generally used are
organic compounds such as thiosulfates (including sodium
thiosulfate, ammonium thiosulfate, potassium thiosulfate and others
readily known in the art), thiocyanates (such as sodium
thiocyanate, potassium thiocyanate, ammonium thiocyanate, amines,
halides and others readily known in the art (such as those
described by Haist, Modern Photographic Processing, John Wiley
& Sons, N.Y., 1979). Mixtures of one or more of these classes
of photographic fixing agents can be used if desired. Thiosulfates
and thiocyanates are preferred. In some embodiments, a mixture of a
thiocyanate (such as sodium thiocyanate) and a thiosulfate (such as
sodium thiosulfate) is used. In such mixtures, the molar ratio of a
thiosulfate to a thiocyanate is from about 1:1 to about 1:10, and
preferably from about 1:1 to about 1:2. The sodium salts of the
fixing agents are preferred for environmental advantages.
The fixing composition can also include various addenda commonly
employed therein, such as buffers, fixing accelerators,
sequestering agents, swelling control agents, and stabilizing
agents, each in conventional amounts. In its aqueous form, the
fixing composition generally has a pH of at least 4, preferably at
least 4.5, and generally less than 6, and preferably less than
5.5.
In processing black-and-white photographic materials, development
and fixing are preferably, but not essentially, followed by a
suitable washing step to remove silver salts dissolved by fixing
and excess fixing agents, and to reduce swelling in the element.
The wash solution can be water, but preferably the wash solution is
acidic, and more preferably, the pH is 7 or less, and preferably
from about 4.5 to about 7, as provided by a suitable chemical acid
or buffer.
After washing, the processed elements may be dried for suitable
times and temperatures, but in some instances the black-and-white
images may be viewed in a wet condition.
Exposure and processing can be undertaken in any convenient
conventional manner. Some exposure and processing techniques are
described in U.S. Pat. Nos. 5,021,327; 5,576,156; 5,738,979,
5,866,309, 5,871,890, 5,935,770, and 5,942,378. Such processing can
be carried out in any suitable processing equipment
The final step in forming the image is to scan the image resulting
form development processing and using an image enhancement
algorithm to arrive at the final image. Conventional scanning
techniques can be employed, including point-by-point, line-by-line
and area scanning, and require no detailed description. A simple
technique for scanning is to scan the photographically processed
element point-by-point along a series of laterally offset parallel
scan paths. The intensity of light received from or passing through
the photographic element at a scanning point is noted by a sensor
which converts radiation received into an electrical signal. The
electrical signal is processed and sent to memory in a digital
computer together with locant information required for pixel
location within the image.
A convenient form of scanner can consist of a single multicolor
image sensor or a single set of color sensors, with a light source
placed on the opposite side of the film. Light transmitted through
the film can give information on the image pattern in the emulsion
layer(s) modulated by the color filter array.
Various methods of image processing may be employed. A relatively
simple method is to represent the image data in a color model which
has a luminance or lightness component and two chromatic or color
components, such as the CIE L*a*b model. The chromatic components
are then blurred with a suitable image filter to remove the higher
frequency color information which arises largely from the color
filter array, and the blurred chromatic information recombined with
the original luminance information. The color saturation of the
image may be varied by altering the contrast of the chromatic
components. Other methods of image processing may be employed
After image processing, the resulting representation of the scene
recorded by the method of the invention may be viewed on a screen
or printed by suitable means to give a printed photographic
image.
The multilayered article of the invention is preferably prepared by
coating and drying on the support the indicated layers in the
desired sequence, as conventionally done in the manufacture of
photographic film. Subbing layers and adhesive layers may be
employed where appropriate.
In operation, the red portion of an image would be reproduced in
the following manner using reversal processing and additive color
beads of red, green, and blue, the formation of a red portion of
the original would proceed as follows:
1. Red light is permitted to pass through (red) bead 6 and create a
latent image on the light sensitive layer 2 of the film.
2. The resulting latent image is reversal developed so that there
is no silver beneath the red bead but there is silver beneath other
red beads where there is no red in the original image.
3. A red laser is used to scan the film and is transmitted through
the film only where there is a red bead and no silver below it
(i.e. where there is a red image in the original) and information
on the location of the relevant red color areas is saved.
4. Image enhancement software is then used to provide the finished
reproduction.
The invention is further illustrated by the following examples.
EXAMPLE 1
In this example we describe in detail our numerical simulation to
produce random two-dimensional coatings of beads and to measure the
resulting fluctuations in these coatings. We approximate the beads
by spheres and we assume they are coated in a monolayer with no
overlap. In this case, we can represent the beads by their
cross-sectional area and thus this monolayer by a two-dimensional
array of colored discs. The discs will be coated at a given area
fraction and ratio of different bead colors in a two-dimensional
square.
For our system of beads of sizes of 3 to 6 microns in diameter, we
have chosen the square to be 500 microns on a side. As is common in
performing these types of simulations, we have chosen to use
periodic boundary conditions on the square in order to prevent
artifacts associated with the edges of the simulated coating. The
size of the system allows for quite good statistics and, to further
improve our statistics, we have performed averages over 10
different simulated coatings when we have quantitatively analyzed
the system.
An initial configuration of discs is chosen to be either a regular
array or a configuration produced by a random insertion method. In
the random insertion method, discs are put down one-by-one at
random subject to the condition of no overlap with any other discs
already put down. The advantage of the random-insertion method is
that the configuration produced is much more random than a regular
array (and thus needs fewer subsequent Monte Carlo randomization
trials. However, the disadvantage is that there is a maximum area
fraction (or "packing density") of discs that can be obtained via
this method and, depending on the desired area fraction and on the
size distribution of the discs, this maximum area fraction is
sometimes less than the desired fraction. If this maximum fraction
is only modestly less than the desired area fraction, a "trick" can
sometimes be played whereby a small amount of overlap of the discs
is allowed, with this overlap then be resolved in the subsequent
Monte Carlo randomization trials.
Once this initial configuration has been obtained, it is randomized
to produce the final simulated bead coating. This randomization is
carried out by a standard Monte Carlo method. In this method, a
disc is chosen at random and it is attempted to move this disc by a
random amount in a random direction, represented by a vector chosen
randomly from the area within a circle of some fixed radius
r.sub.max. This move is accepted provided the disc in question does
not overlap any other disc following such a move; otherwise, it is
rejected. The radius r.sub.max of the circle from which the vector
is chosen represents the maximum distance that a disc might be
moved in such a trial. The Monte Carlo algorithm is typically found
to be most efficient at randomizing the system if this r.sub.max is
chosen so that somewhere on the order of half the moves are
accepted; we find that a radius of 0.2 or 0.25 times the largest
disc diameter is typically sufficient to satisfy this rough
criterion.
Each attempt to move one disc is considered to be one trial (or
"step"). One must have a sufficient number of trials in order to
produce a random distribution of discs (subject to the no-overlap
constraint) from the initial configuration. The best way to insure
that the number of trials is sufficient is to compare statistical
measures of the simulated coating (such as the Wiener spectrum
described below) for coatings which are started from different
types of initial configurations (such as a regular array versus
those produced by the random insertion method) or coatings produced
from the same initial configurations but run for a very different
number of Monte Carlo trials. We have typically used a number of
trials equal to 3000 to 10000 times the number of beads in the
coating and have verified in several cases that this is far more
than sufficient to produce a random configuration.
To study the quality of our simulated bead coatings quantitatively,
we employ standard techniques from the image science literature [J.
C. Dainty and R. Shaw, Image Science: Principles, Analysis, and
Evaluation of Photographic-type Imaging Processes, Academic Press,
N.Y., 1974]. In particular, we define a circularly-averaged Wiener
spectrum by first computing the full two-dimensional Wiener
spectrum according to Dainty and Shaw, Chapter 6, Eq. (43) and then
taking advantage of the isotropic nature of the system to
circularly-average and obtain the spectrum as a function of one
radial coordinate. We compute the Wiener spectrum for four
different quantities; W.sub.R, W.sub.G, and W.sub.B correspond to
the spectrum for red, green, and blue beads, respectively, whereas
W.sub.all corresponds to the spectrum for all beads without respect
to bead color. For W.sub.R, we define the quantity .DELTA.D(x,y)
that appears in Dainty and Shaw, Chapter 6, Eq. (43) to be given by
D(x,y)-<D(x,y)> where D(x,y)=1 if a red bead covers the point
(x,y) and D(x,y)=0 if it does not, and <. . .> denotes the
average of this quantity over the two-dimensional space. W.sub.G
and W.sub.B are computed in an analogous manner and W.sub.all is
similar except that D(x,y)=1 if any color bead covers the point
(x,y).
The plots of this entire Wiener spectrum shows the magnitude of the
fluctuations as a function of the spatial frequency; however, the
most important fluctuations are those at low enough spatial
frequencies that these fluctuations occurring in the film will be
detectable by the human eye in the final image. For this purpose,
we adopt a measure analogous to a standard measure of granularity
in color negative film. In particular, the granularity G measured
through a circular aperture of radius r is related to the
circularly-averaged Wiener spectrum W(.omega.) by ##EQU1##
where J.sub.1 (x) is the 1.sup.st -order Bessel function [see
Dainty and Shaw, Chapter 8, Eq. (14)]. We take the aperture
diameter to be 2r=48 microns. This measure is thus related to a
weighted average of the Wiener spectrum with the weighting
emphasizing those spatial frequencies below about 20 mm.sup.-1.
It is emphasized that the resulting G.sub.R, G.sub.G, G.sub.B, and
G.sub.all measure those noise fluctuations for each of the
different colored beads and for all the beads as a whole that are
thought to be most relevant in determining the noise visible to a
viewer of the final image obtained from the random CFA film.
Although these are defined in analog to definitions of granularity,
they are not direct measures of the granularity of the film itself.
Nonetheless, they are expected to be rough correlates of this.
For our first numerical study we consider the effect on the noise
fluctuations of taking a certain fraction of the beads (chosen
irrespective of their color) and reducing them in size by a factor
of two, from 6 microns to 3 microns. In each case, the total areal
coverage of the beads is 60% and the ratio of red, green, and blue
beads is R:G:B=42%:29.5%:28.5%. Table I below summarizes the
results where the first column represents the fraction of the beads
(by area fraction, not number of beads):
TABLE I % small by area fraction G.sub.R G.sub.G G.sub.B G.sub.all
0 control 1.91 1.80 1.76 0.80 2.7 control 1.92 1.81 1.76 0.81 9.7
control 1.91 1.72 1.70 0.80 27 invention 1.76 1.63 1.58 0.76 50
invention 1.63 1.41 1.46 0.74
The results show that with up to the 10% coverage fraction of small
beads, there is little change in the noise. However, by 27%
coverage, there is a small but significant decrease in the noise.
By 50% coverage, the decrease in the noise is more dramatic. For a
sense of scale here, it is useful to recall that a 5% increase in
the value of G corresponds to one grain unit.
For our second numerical study we consider the effect on the noise
fluctuations of reducing the size of all the beads of one or more
colors by a factor of two, from 6 microns to 3 microns. In each
case, the total areal coverage of the beads is .about.60% and the
areal coverage of the red, green, and blue beads is equal. Table II
below summarizes the results:
TABLE II which color beads are small: G.sub.R G.sub.G G.sub.B
G.sub.all none control 1.85 1.90 1.84 0.80 R invention 0.88 1.69
1.51 0.70 R, G invention 0.81 0.93 1.44 0.67 all invention 0.92
0.94 0.92 0.38
These results illustrate how a reduction in the size of a given
bead color by a factor of 2 results in a decrease of the noise
fluctuations in the bead laydown for the beads of that color also
by about a factor of 2. Moreover, there is a less pronounced, but
still significant, decrease in the noise fluctuations for the other
bead colors too. Thus, significant noise-reduction advantage can be
gained by reducing the size of even one, and even more so two, of
the three colors of beads.
In order to confirm that the decrease in noise fluctuations of the
distribution of beads themselves translates into a decrease in the
noise of the final image, we have taken samples of each of the
above numerically-produced bead laydowns and have run them through
a simulation of the exposure, processing, scanning, and printing of
an ideal negative-working random CFA film. We assume a uniform
exposure over the entire 500 micron by 500 micron coating. In this
simulation, for example, exposure with red light results in
development of silver under the red beads and no development
anywhere else. The resulting negative thus looks black in regions
where red beads are and is blue or green in regions where the blue
or green beads are, respectively. The area between beads can be
treated in various ways depending on one's assumptions regarding
the existence and concentration of a nano-particulate dispersion,
such as carbon black particles, in the binder between the beads.
The scanning step is simulated by blurring this image over an
appropriate distance, such as 12 microns; this represents the
resolution of the scanning aperture. Finally, the color of the
image is reversed in order to simulate the reversal step in
producing the final print.
The above-described simulation is an idealized version of any
experimental realization of a random CFA film in a variety of ways.
For example, it assumes that the dyes in the beads are perfect
"block" dyes, that the resolution of the light-sensitive layer is
unlimited (i.e., the emulsion grains are very small), that the
light is and remains perfectly-collimated, etc. Nonetheless, the
results of these simulations show that decreases in the noise
parameters G.sub.R, G.sub.G, G.sub.B, and G.sub.all for the
distribution of the beads do indeed correlate with decreases in the
noise in the final image.
For further confirmation that the claims of our invention lead to a
significant reduction in the noise, we have studied an experimental
example of our random CFA film. This experimental example has also
allowed us to relate the size of the beads to the size of the
emulsion grains in the light-sensitive layer.
EXAMPLE 2
This example illustrates the effect of selectively reducing the
size of one or more of the micro-filter elements (R, G, or B) on
noise in a color print prepared by exposing a color filter array
(CFA) scan film with said micro-filter elements to a scene,
processing the exposed film, scanning the processed film using a
suitable scanner to convert the image into an electronic form that
can be stored and manipulated on a computer, enhancing color levels
in the electronic form using image processing software such as
Adobe Photoshop and then printing the final image using a suitable
thermal or inkjet printer.
Preparation of Colored Beads or Micro-Filter Elements:
Red Beads 1 (RB1):
Twenty-five grams of a 47.6% w/w suspension of polystyrene beads
prepared by limited coalescence (having mean diameter of 6 microns)
was combined with 25 grams of distilled water and 5 grams of
poly(vinyl alcohol) (75% hydrolyzed, molecular weight 3000) to
constitute a diluted latex suspension. The "Limited Coalescence"
process was described previously.
Dye 1 (0.5 grams), 0.5 grams of Neptun Yellow 075 from BASF
Corporation, an organic soluble azo-dye with a spectral absorption
maximum of 450 nm, in toluene and 0.225 grams of Sudan Orange 220
from BASF Corporation an organic soluble azo-dye with a spectral
absorption maximum of 474 nm in toluene were dissolved in 0.5 grams
of toluene and 49.5 grams of acetone. The diluted latex suspension
was then added slowly (drop-wise) to this solution of the dyes
while stirring to prepare a dyed latex suspension. The dyed latex
suspension was then filtered using a porous cotton filter, poured
into a dialysis bag (12,000 to 14,000 molecular weight cutoff) and
washed with distilled water for one hour. After washing, the dyed
latex suspension was filtered again using a porous cotton filter.
The washed and filtered dyed latex suspension was centrifuged to
provide a concentrated aqueous suspension of red colored polymer
beads suitable for coating (15% w/w beads).
Blue Beads 1 (BB1):
Dye 2 (0.7 grams) and 0.55 grams of Dye 3 in were dissolved in 0.5
grams of toluene and 49.5 grams of acetone. The remainder of the
preparation was similar to that of the red colored beads RB1.
Green Beads 1 (GB1):
Dye 3 (0.45 grams) and 0.495 grams of Neptun Yellow 075 were
dissolved in 0.5 grams of toluene and 49.5 grams of acetone. The
remainder of the preparation was similar to that of the red colored
beads RB1.
Red Beads 2 (RB2):
Atlox 4991 (0.2 grams) from Uniqema, Wilmington Del. was combined
with 10 grams of surfactant-free white polystyrene latex beads at a
concentration of 8% w/w (mean diameter 3.1 microns, standard
deviation of diameter 0.11 from Interfacial Dynamics Corporation,
Portland, Oreg.; the size of the beads being just larger than the
size of the largest emulsion grains).
Dye 1 (0.033 grams), 0.033 grams of Neptun Yellow 075 and 0.225
grams of Sudan Orange 220 were dissolved in 0.1 grams of toluene
and 9.9 grams of acetone. The suspension of polystyrene beads
containing Atlox was then added slowly to this solution of dyes.
The dyed latex suspension was then filtered using a porous cotton
filter, poured into a dialysis bag (12,000 to 14,000 molecular
weight cutoff) and washed with distilled water for one hour. After
washing, the dyed latex suspension was filtered again using a
porous cotton filter. The washed and filtered dyed latex suspension
was centrifuged to provide a concentrated aqueous suspension of red
colored polymer beads suitable for coating (3% w/w beads).
Blue Beads 2 (BB2):
Dye 2 (0.037 grams) and 0.0.29 grams of Dye 3 were dissolved in 0.1
grams of toluene and 9.9 grams of acetone. The remainder of the
preparation was similar to that of the red colored beads RB2.
Spectral analysis of the light transmission properties of the three
colors of beads showed that each color of beads was sufficient to
transmit light primarily in the desired color range.
CFA scan films comprising the above colored particles were prepared
as follows:
The following black and white emulsion layers were first coated on
a cellulose triacetate film support having a carbon anti-halation
backing (coverages are in grams per meter squared, emulsion sizes
as determined by the disc centrifuge method are reported in
diameter.times.thickness in micrometers). Surfactants, coating aids
and emulsion addenda were added as is common in the art. Layer 1
(slow layer): a blend of three dyed (all with mixtures of SD-1 and
SD-2) tabular silver iodobromide emulsions: (i) 1.30.times.0.12,
4.1 mole % I at 0.80 (ii) 0.66.times.0.12, 4.1 mole % I at 1.20
(iii) 0.55.times.0.08, 1.5 mole % I at 1.20; CHEM-1 at 1.50; and
gelatin at 4.10. Layer 2 (fast layer): a dyed (with a mixture of
SD-1 and SD-2) tabular silver iodobromide emulsion 2.61.times.0.12,
3.7 mole % I at 1.40; CHEM-1 at 0.70; and gelatin at 1.80.
A sublayer or undercoat layer containing 1.08 g/m.sup.2 of acid
processed ossein gelatin was coated above the emulsion layers. The
suspensions of colored beads were combined with lime processed
ossein gelatin and an aqueous nano-particulate dispersion of carbon
black obtained by milling commercially available carbon black Black
Pearls 880 from Cabot Corp. to a mean size below 100 nm using a
conventional media mill with 50 micron polymeric beads and spread
over the above emulsion layers to provide CFA films. The following
films were made:
Film 1: (Control)
CFA layer containing 2.58 g/m.sup.2 beads (equal parts of RB1, GB1,
and BB1), 0.22 g/m.sup.2 carbon black and 0.52 g/m.sup.2 gelatin.
An overcoat containing 1.08 g/m.sup.2 gelatin was coated above the
CFA layer.
Film 2: (Invention)
CFA layer containing 0.86 g/m2 of GB1, 0.43 g/m.sup.2 RB2 and 0.43
g/m.sup.2 BB2. The remainder of the layer composition was similar
to that of Film 1.
Analysis of micrographs of the CFA in these two cases was carried
out in a manner analogous to the analysis of the simulated coatings
that was described in Example 1. The results for the measure of
granularity are summarized in the table below and show the superior
noise characteristics of the CFA of Film 2 in comparison to the CFA
of Film 1. Note that, as in Example 1, the reduction in the noise
of the bead distribution is greatest for those colors of beads
whose size is reduced but that a reduction in the noise is also
achieved for the green beads whose size is not reduced.
TABLE III G.sub.R G.sub.G G.sub.B G.sub.all Film 1 control 2.57
2.37 2.73 3.01 Film 2 invention 1.71 2.16 1.89 2.36
The above films were exposed to a scene in a studio using a Minolta
XG7 SLR camera. The films were then Black and White processed at
34.8.degree. C. using developer of the following composition.
Sodium carbonate 25.1 g/L Sodium sulfate 5.0 g/L Glycine 25.1 g/L
MOP(4-hydroxymethyl-4methyl-1-phenyl-3pyrazolidinone) 1.5 g/L
Sodium bromide 1.0 g/L
The exposed films were immersed in the developer for one minute
followed by one minute in a 3% acetic acid stop bath, washed in
running water for three minutes, and then immersed for five minutes
in a C-41 fixer followed by a final wash for five minutes.
The processed negatives were scanned using a Kodak RFS3750 film
scanner and then electronically color enhanced using Adobe
Photoshop software version 5.0. Prints were then obtained from the
color enhanced images using a Kodak Professional 8670 PS thermal
printer.
A comparison of prints obtained from Film 1 (control) and Film 2
(invention) showed considerably reduced noise in the latter case.
##STR1##
The entire contents of the patents and other publications referred
to in this specification are incorporated herein by reference.
PARTS LIST
1 Support 2 Light Sensitive Layer 3 Under Layer 4 Color Filter
Array (CFA) Layer 5 Protective Overcoat 6 Transparent Bead of First
Color 7 Transparent Bead of Second Color 8 Transparent Bead of
third Color 9 Water permeable Continuous Phase Transparent Binder
10 Neutral Nano-Particle
* * * * *